(a) Technical Field
The present disclosure relates to a fail-safe control method for an oil pump control unit of a hybrid vehicle. More particularly, it relates to a fail-safe control method, which can ensure driving performance by a fail-safe or limp-home control in the event of a failure of an electric oil pump for a hybrid vehicle, an oil pump control unit, or a CAN communication line.
(b) Background Art
In a hybrid vehicle, a mechanical oil pump mounted in the automatic transmission (ATM) can supply hydraulic pressure to the automatic transmission only when the vehicle is driven (automatic transmission input speed>600 rpm, for example).
An external electric oil pump (OP) mounted in the hybrid vehicle generates hydraulic pressure (e.g., 10.5 bar) in a hydraulic circuit (valve body) in the automatic transmission and in the engine clutch even in the event that an engine is stopped such as in electric vehicle (EV) mode, idle stop mode, etc.
In EV mode in which the hybrid vehicle is driven only by the electric motor, since the output torque of the electric motor is transmitted to an output shaft through the automatic transmission, it is necessary, when the engine is stopped, to apply a predetermined torque capacity to the automatic transmission by receiving the hydraulic pressure from the electric oil pump.
However, in the event that the engine of the hybrid vehicle is driven at a low speed (e.g., driven at less than about 600 rpm) or stopped, if a motor of the electric oil pump is off due to its failure or due to a failure of a CAN communication line or an oil pump control unit, the supply of hydraulic pressure to the automatic transmission and the engine clutch becomes zero or insufficient, and thus the output of the electric motor may not be transmitted to an output member. Consequently, it may be impossible to drive the vehicle, perform a fail-safe or limp-home control, and ensure desired driving performance.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.